The art of field navigation involves the use of certain devices whereby readings related to current position, directional heading, and the like are determined and are rendered available for a user operating such a device. There are many navigational systems and devices that range from relatively inexpensive compass-type devices to expensive satellite systems used by such as military personnel. The device most used by individuals for navigation in the field is the traditional compass.
By utilizing a simple hand-held compass and a map, an individual with certain skill is able to navigate in unfamiliar terrain. However, with a traditional mechanical compass, operators must manually calculate additional information by virtue of using additional instruments if more information than a simple direction heading is desired or needed. For example, a watch is needed to determine time traveled in any one direction. An inclinometer may be required, along with a calculator or mathematical table, to gage distance.
Other information may be obtained through the use of yet additional devices that may enhance or compliment field navigation with a compass. For example, altimeter information, barometric information, humidity readings, and the like may aid a user with a compass to optimize navigation through difficult terrain. An obvious drawback exists in that adding all of the additional equipment increases expense for a user in the field. Moreover, such equipment requires additional space to carry and can burden a single user who may be navigating alone. Furthermore, having many additional devices, some of which are delicate, increases the chance of damaging such instruments inadvertently during operational use or transport.
More recently, digital compasses have been introduced that eliminate some of the requirements associated with manual compasses. For example, U.S. Pat. No. 4,851,775, hereinafter referred to as Kim, provides an electronic compass that utilizes a magnetic-sensing technology that is responsive to the earth's magnetic field. In this way, an electronic display may provide directional indication that is more accurate and faster registering than manual compass readings. U.S. Pat. No. 5,239,264, hereinafter referred to as Hawks, enhances the prior technology by providing better sensing capability and introducing a magnetic interference cancellation technology that eliminates interference from alternate magnetic sources other than the earth's field. Accuracy is improved by analyzing and comparing different oscillation periods and performing calculations to eliminate unwanted deviation from true readings (drift). Much technical information regarding the exact circuitry and function of these compasses may be reviewed in the above-mentioned Patents.
Still another enhancement to digital compass technology is the ability to set and record a reference heading into compass memory. A reference-heading indicator may be a bracketed reference needle on a LCD display. This improvement is disclosed in U.S. Pat. No. 5,381,603 entitled Reference Pointer For a Compass Display issued on Jan. 17, 1995 to John S. Lee.
One important factor to consider in providing a digital compass that is affordable to a normal user and small enough to be hand-held, is the ability to provide a simple compact circuitry wherein individual components are readily available. The Patents cited above meet the requirements for compact and simple circuitry. However, the above references are still limited in that other functions related to navigation are not available to those compasses.
It is desirable, when in the field, that a minimum amount of devices be used to perform a maximum amount of functions wherein the functions are used singly or in combination to optimize a navigational experience. Therefore, what is needed is a digital compass with multiple sensor and calculating capabilities that may be used to take multiple readings to be used singly or in combination to enhance or optimize the navigator's experience. Such a device would eliminate the requirement of taking along additional instruments and subsequently lower the cost of navigating for most users. Moreover, by incorporating the additional sensors into the single instrument, the sensors may be integrated to provide more information than a single sensor alone could provide.